<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Document</title>
    <style type="text/css" media="screen">
        #box1{
            width: 100px;
            height: 100px;
            background-color: red;
        }
        #box2{
            width: 10px;
            height: 100px;
            background-color: black;
        }
        #box3{
            width: 300px;
            height: 400px;
            background-color: yellow;
        }
    </style>
</head>
<body>
    <div id="box1"></div>
    <div id="box2"></div>
    <div id="box3"></div>
</body>
<script src = "wang.js"></script>
</html>